Purpose: This study examined the acute effects of lower-body high-intensity interval loading (HIIT) on explosive upper- and lower-body strength, as well as the combined effect of HIIT and bench-press loading versus HIIT and squat loading on the explosive upper- and lower-body strength.
Methods: Fifteen physically active men completed 2 sessions consisting of HIIT (4 × 4 min cycling at 80% of peak power output) immediately followed by lower- (HIIT + LBS) or upper-body (HIIT + UBS) strength loading (3 × 5 + 3 × 3 repetitions at 80% 1-repetition maximum [ie, 6 sets in total]) in a randomized order. Squat and bench-press mean propulsive velocity (MPV) was assessed before HIIT (T0), immediately after HIIT (T1), immediately after the strength loading (T2), and 24 hours after the experimental session (T3).
Results: Squat MPV decreased to a similar magnitude at T1 in HIIT + LBS (-5.3% [7.6%], P = .117, g = .597) and HIIT + UBS (-5.7% [6.9%], P = .016, g = .484), while bench press remained unchanged (-1.4% [4.7%], P = 1.000, g = .152, and -1.0% [7.0%], P = 1.000, g = .113, respectively). Both squat and bench-press MPV were statistically reduced at T2 compared to T0 (HIIT + LBS: -7.5% [7.8%], P = .016, g = .847, and -6.8% [4.6%], P < .001, g = .724; HIIT + UBS: -3.9% [3.8%], P = .007, g = .359, and -15.5% [6.7%], P < .001, d = 1.879). Bench-press MPV at T2 was significantly lower in HIIT + UBS when compared to HIIT + LBS (P = .002, d = 1.219).
Conclusion: These findings indicate lower- but not upper-body explosive strength to be acutely reduced by preceding lower-body HIIT. However, lower-body HIIT combined with either upper- or lower-body strength loading resulted in a similar acute reduction of both squat and bench-press explosive strength.
Keywords: concurrent training; high-intensity interval training; strength training.